try not to 'over' think it. im sure you will meet and make friends with other students in time, maybe they are quieter and anxious about going back to school as well. i understand as i am agoraphobic, although my meds control it, but id be anxious too. you are not alone. if it gets too tough, jump on here and have a word with your HW friends- we are here to support you every step of the way.
AS a high school teacher, i see plenty of kids who start out anxious and unsettled- but in time they DO make friends and settle in. i really hope things get better for you and am thinking of you. remember- you can always come here-
keep us posted on how you go- i think you are anticipating the worst, when in reality, when you get there, it wont be that bad.